Coordination of Duplex Directions in Nr Tdd System

1. A method performed by a network node operating as a joint traffic direction scheduler of a coordination group including multiple cells, comprising: obtaining time-division duplexing (TDD) operation information from each cell included in the coordination group; determining, based on the obtained TDD operation information, a transmission direction to be used by each of the cells during one or more transmission time intervals (TTIs), wherein determining the transmission direction comprises detecting the change of the ratio of downlink-to-uplink traffic and switching one or more TDD modes in response to the ratio crossing a threshold; and indicating to the cells the determined transmission direction.

2. The method of claim 1, wherein indicating the determined transmission direction comprises signaling that one or more predetermined TDD modes is to be used or is not to be used by one or more of the multiple cells.

3. The method of claim 2, wherein the one or more predetermined TDD modes indicates a predetermined ratio of downlink-to-uplink (DL:UL) transmissions to be used by the one or more of the multiple cells.

4. The method of claim 2, wherein the one or more predetermined TDD modes comprises a fully dynamic TDD mode.

5. The method of claim 2, wherein the one or more predetermined TDD modes comprises a hybrid dynamic TDD mode in which a scheduling restriction is imposed within a part of dynamic TDD duration.

6. The method of claim 2, further comprising signaling a duration of the one or more predetermined TDD modes.

7. The method of claim 1, wherein determining the transmission direction to be used by each of the cells during the one or more TTIs comprises one or more of: detecting a buffer status change for one or more of the cells; detecting a buffer status for one or more of the cells; detecting a change of a ratio of downlink-to-uplink (DL:UL) traffic in one or more buffers; and detecting a change of a quality of service (QOS) type to be applied to traffic associated with one or more of the cells.

8. The method of claim 7, wherein determining the transmission direction comprises detecting the buffer status change, and detecting the buffer status change comprises: receiving a periodic or event-based report; and determining whether one or more of the cells have upcoming traffic for both uplink (UL) and downlink (DL) directions.

9. The method of claim 1, further comprising sending a first mode selection signal to the cells to trigger the use of a dynamic TDD mode when all of the cells are to transmit data in the same TDD traffic direction during the one or more TTIs, else sending a second mode selection signal to the cells to trigger the use of a static TDD mode when not all of the cells are to transmit data in the same TDD traffic direction during the one or more TTIs.

10. The method of claim 1, further comprising one or more of the cells switching from a current time-division-duplex (TDD) mode to a new TDD mode based on the indication.

11. A method performed by a network node operating as a joint traffic direction scheduler of a coordination group including multiple cells, comprising: obtaining time-division duplexing (TDD) operation information from each cell included in the coordination group; determining, based on the obtained TDD operation information, a transmission direction to be used by each of the cells during one or more transmission time intervals (TTIs); in response to determining that the direction of the traffic is the same for each of the multiple cells during the one or more TTIs, controlling the multiple cells to operate according to a dynamic TDD mode by indicating to the cells the determined transmission direction; and in response to determining that the direction of the traffic is not the same for each of the multiple cells during the one or more TTIs, controlling the multiple cells to operate according to a static TDD mode by indicating to the cells the determined transmission direction.

12. The method of claim 11, wherein the multiple cells are co-located.

13. A network node comprising a joint traffic direction scheduler configured to coordinate time-division-duplexing (TDD) transmissions for multiple cells, comprising: processing circuitry, memory, and at least one transceiver collectively configured to: obtain TDD operation information from each of the cells; determine, based on the obtained TDD operation information, a transmission direction to be used by each of the cells during one or more transmission time intervals (TTIs), wherein determining the transmission direction comprises detecting the change of the ratio of downlink-to-uplink traffic and switching one or more TDD modes in response to the ratio crossing a threshold; and indicate to the cells the determined transmission direction.

14. The network node of claim 13, wherein determining the transmission direction to be used by each of the cells during the one or more TTIs comprises one or more of: detecting a buffer status change for one or more of the cells; detecting a buffer status for one or more of the cells; detecting a change of a ratio of downlink-to-uplink (DL:UL) traffic in one or more buffers; and detecting a change of a quality of service (QOS) type to be applied to traffic associated with one or more of the cells.

15. The network node of claim 14, wherein determining the transmission direction comprises detecting the buffer status change, and detecting the buffer status change comprises: receiving a periodic or event-based report; and determining whether one or more of the cells have upcoming traffic for both uplink (UL) and downlink (DL) directions.

16. The network node of claim 13, wherein the processing circuitry, memory, and at least one transceiver are further collectively configured to send a first mode selection signal to the cells to trigger the use of a dynamic TDD mode when all of the cells are to transmit data in the same TDD traffic direction during the one or more TTIs, else send a second mode selection signal to the cells to trigger the use of a static TDD mode when not all of the cells are to transmit data in the same TDD traffic direction during the one or more TTIs.

17. The network node of claim 13, wherein the processing circuitry, memory, and at least one transceiver are further collectively configured to control the multiple cells to switch between a dynamic time-division-duplexing (TDD) mode and a static TDD mode, comprising: determining a direction of traffic to be scheduled for each of the multiple cells during one or more TTIs; in response to determining that the direction of the traffic is the same for each of the multiple cells during the one or more TTIs, controlling the multiple cells to operate according to a dynamic TDD mode; and in response to determining that the direction of the traffic is not the same for each of the multiple cells during the one or more TTIs, controlling the multiple cells to operate according to a static TDD mode.

18. The network node of claim 13, wherein the network node is a baseband processor covering a remote radio unit for each of the multiple cells.